Poly(alpha-olefin) (PAOs) fluids are commercially employed as base stocks in lubricant products. PAOs have many advantages compared to conventional mineral oils and Group III/III+ lubricants. More specifically, PAOs have superior VI (viscosity index), low temperature properties (CCS, MRV, etc.), pour points, and low traction, which translates into better energy efficiency and additive response and complete miscibility in conventional mineral oils. Performance limitations of PAOs include a lack of polarity, which impacts ability to solubilize polar additives, such as antioxidants, anti-rust agents and anti-wear agents. Conventionally, polar organic esters have been added to PAO lubricants to render them compatible. Useful commercial formulations may have 2% or more of such esters in a fully homogeneous lubricant blend. Examples of such esters include, for example, bis-tridecanol adipate and pentaerythritol hexanoate.
Polyalkylene glycol (PAG) fluids have also been employed as lubricant base stocks. Their performance advantages are high VI, good lubricity (in hydrodynamic, mix, and boundary lubrication conditions), and excellent cleanliness. Some grades are even considered acceptable for incidental food contact (H1 grade). Performance limitations include lack of miscibility and compatibility with conventional mineral and hydrocarbon-based lubricants as well as high solubility in water, which results in severe corrosion problem. Some PAGs have paint or seal compatibility problems. The formulation or additive response of PAGs with respect to additives can be unpredictable, rendering them difficult to formulate with.
It would be desirable to have lubricant base stocks that had the performance advantages of both PAOs and PAGs without their limitations. It would also be desirable to have lubricant base stocks that can be readily blended with conventional lubricant base stocks.